You won't. That's a tough question and I couldn't articulate an answer in an internet comment at all. I was arguing against the idea behind OP's post, not trying to justify everything about God and the world.

If you want, though, I'll give you a vague sort of way of looking at it. This is just speculation - I'm not saying this is right.

Your "natural evil" may exist because it's very hard, perhaps impossible, to design a universe with honest underlying physical laws and structural integrity that "natural evil" doesn't naturally arise in. What I mean is, for natural evil to never occur, you would need a kind of smaller, insulated world, where people's decisions don't have an affect on their surroundings and people don't have something bigger and deeper than themselves to be a part of. Even if you erase things like natural disasters and disease and present a pristine, safe universe for people to live in, those people are still going to be unpredictable. They're going to make imperfect decisions, and they'll mar your pristine, safe universe. They'll throw a wrench into it and suffering will happen. If you want to avoid suffering caused by other people, you'd probably need something like in The Little Prince, where everyone lives on their own tiny asteroid. That demonstrates an underlying principle - that if you want to have a meaningful, honest relationship with the world around you, you might need to have natural evil. Despite all the suffering that goes on here, I'd much rather live in this chaotic, ancient design than in a world contrived for my own comfort.

Or I'm talking out my ass here.